U.S. Pat. Nos. 3,576,517 and 3,892,458 disclose typical circular electrical connectors of the general type comprising an insulating housing, a metallic shell in surrounding relationship to the housing, and a coupling ring rotatably mounted on the cylindrical shell of one of the connector parts. The coupling ring has screw threads or slots on its internal surface for cooperation with screw threads, or a bayonet type pin on the surface of the shell of the complementary connector part so that when the two connector parts are mated, rotation of the coupling ring will serve to draw the two parts into engagement with each other. The coupling ring further serves to maintain the connector parts in mated relationship and prevent unmating as a result of vibration or other factors.
Electrical connector assemblies of the type shown in the above identified U.S. patents are widely used under circumstances where an extremely high quality and highly reliable connector is required, for example, in aircraft for connections in critical circuits. Connectors of this type are extremely costly as the result of the extremely high manufacturing costs. The metallic shell for connectors of the type disclosed in the above patents and the coupling rings are, for example, produced by impact extrusion, machining, and investment casting processes, all of which are extremely expensive manufacturing methods.
It would be desirable to produce high performance circular electrical connectors at a greatly reduced manufacturing cost, however, it has not been deemed practical heretofor to substitute low cost materials for the materials presently being used in circular connectors, nor has it been deemed practical to resort to manufacturing methods which are less costly than the manufacturing and processing methods currently used to produce circular electrical connector parts. The reluctance to attempt to use alternative and lower cost manufacturing methods probably stems from the rigid requirements and performance characteristics demanded for connectors used in critical circuits. The coupling ring, for example, is an essential element of a high quality electrical connector and represents a substantial portion of the manufacturing cost of the completed connector. The coupling ring must be of a relatively thick metal and must be capable of withstanding abusive and careless treatment without interference with its function. For this reason, the coupling rings of presently available circular connectors are produced by combination of impact extrusion and machining operations, which are inherently high cost operations. The metallic shell likewise is a relatively expensive element and is produced by time consuming machining operations.
The present invention is then directed to the achievement of a circular electrical connector which can be produced at a greatly reduced cost. The objectives of the invention are achieved in part by eliminating the need for a separate metallic shell on one of the connector parts and having the coupling ring serve as the shielding function of the shell of prior art connectors as well as the coupling function. The coupling ring is produced as a composite member comprising an outer metallic cylindrical portion and an inner metallic cylindrical portion, concentrically mounted in the outer portion at the leading, or mating, end of the outer portion. The outer portion can be produced by drawing and is dimensioned such that it will overlap the cable clamp which is affixed to the rearward end of the connector housing, thereby providing shielding along the entire length of the connector part. The bayonet slots or threads, if desired, are obtained in the inner cylindrical portion by forming the slots in a flat rectangular blank and thereafter forming the blank into a cylindrical shape. The formed blank is then fitted into the outer cylindrical portion of the coupling ring and welded or fixed in its proper position.